An extracellular sulfated fucose-rich polysaccharide produced by a tropical strain of cryptomonas obovata (cryptophyceae)

Abstract

A tropical strain of Cryptomonas obovata Skuja, isolated from a shallow oxbow lake, released a sulfated fucoserich polysaccharide. The polysaccharide is composed mainly of fucose (42%), N-acetyl-galactosamine (26%) and rhamnose (15%), with small quantities of glucuronic acid, mannose, galactose, xylose and glucose. Sulfate accounted for 1.7% total polysaccharide. Quantitative release was studied with cells exposed to optimal culture conditions contrasted with high irradiance and nitrate depletion. This latter set of conditions could simulate stress situati ons usually found in the place from which this strain was isolated. The monosaccharide composition of the polysaccharide was evaluated using PAD-HPLC and gas chromatography. The two irradiances tested (165 mol m−2 s−1 and 2000 mol m−2 s−1) had no significant effect on amounts of polysaccharide released by the cells. Differences were observed when the nitrate availability was varied. In the nitrate-depleted situation, extracellular polysaccharide production was 2.5 times higher than replete cells after 6 h at 165 mol m−2 s−1, and 2.25 times higher at 2000 mol m−2 s−1.